We propose to characterize intestinal carnitine absorption using a variety of in vitro and in vivo techniques in order to determine the mechanism of carnitine absorption at both physiologic and pharmacologic concentrations. Although oral carnitine has been successfully used to treat patients with systemic carnitine deficiency and has been proposed as therapy for a variety of other disorders, there are no published studies of carnitine absorption by the intestine. Since the recent studies which have implicated impaired renal tubular reabsorption in the pathogenesis of systemic carnitine deficiency suggest also the possibility of an associated intestinal transport defect, we will be especially concerned with comparing intestinal carnitine transport between normal controls and patients with that disorder. Our study may well provide important information bearing on the pathophysiology of this disease.